... 2 Measurement of PMTs counting characteristics and selection of op erating p oint To select the operating point of the PMT, that is the optimal values of the high voltage supply and pulse discrimination threshold, the command run counting=hv value is provided in the program mass. ... Starting with the minimum voltage (say 550 V) run command run counting=550 for the measurement execution. ... It is recommended to take measurements for the set of values of 0.4, 0.6, 0.8, 1.0. ...